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94 vaccum modulator repalced now not shifting

Discussion in 'Stock 1991 - 1994 Explorers' started by paulha, June 16, 2017.

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  1. paulha

    paulha Member

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    I have tried to search for this exact problem, and I either searching wrong or something because I didn't find anything like it, if someone can point me in the right direction or right thread I would appreciate it.
    So, after looking at where the modulator was I opted to have my mechanic do the work. Got the truck back and it has shifting problems, slow to start, high rpms before shifting, downshifts, etc.
    I had none of these problems before I had him replace the modulator, it shifted perfectly, used burned a couple of qts a month but shifted just fine. Any thoughts, I am afraid to drive it much and it is all I have. The mechanic said "it shifts hard but it will smooth out" oh really? Also can someone tell me where the vacuum line from the transmission connects up top? Thanks in advance for any and all help.
    Paul
     
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  3. Rhett

    Rhett Let Them Eat Cake Elite Explorer

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    The vac line runs up to the top of the intake manifold -- there should be a hard line in plain view up there.

    Is it possible that your mechanic forgot about, or dropped, the small metal rod that the modulator hits? If this rod is not reinstalled, you can have a lot of trouble shifting. It is easy to misplace it when you pull the old modulator out.
     
  4. gmbroy

    gmbroy Elite Explorer

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    I have to agree with Rhett , sounds like a vacuum line not hooked up, or the metal rod was lost that is the biggest mistake made when replacing the modulator valve . your mechanic should fix it for free .
     
  5. paulha

    paulha Member

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    Ok here is an update,, it has been a week and the mechanic has been giving me the run around and not only is it hard on my tranny I am getting tired of the run around. Turns out there is an adjustment on the vacuum modulator! Does anyone have any idea how I go about adjusting the modulator? I am really getting desperate so get this up and going, pleease!!
     
  6. Marv

    Marv New Member

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    I put an adjustable vacuum modulator on mine, never needed do any adjusting, works just fine. I would say he dropped the pin out of it and never saw it.
     
  7. paulha

    paulha Member

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    IF that is true, where can I get one? I should know tomorrow, I sure hope it is there.
     
  8. transman304

    transman304 Elite Explorer

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    Why did you replace the modulator? What symptoms were you having?
    Here is a picture of adjustable modulator.
    IMG_3760.JPG
     
  9. paulha

    paulha Member

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    I originally had my mechanic replace the modulator because it was bad and I was burning tranny fluid at the rate of about a quart every two weeks. Before I had him do that it was shifting just fine. Now it won't hardly shift at all, I have to really get the rpms up there for it to shift and then it downshifts, just back and forth through this cycle. He claims that the pin is in there, but then again he left the heatshield just hanging there! So I purchased another one just like the one above and I am going to try to get it in. I can only hope the pin is there otherwise I don't know what to do?
     
  10. Rhett

    Rhett Let Them Eat Cake Elite Explorer

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    If the pin is in there, and your mech installed an adjustable modulator, then I would adjust it -- that may solve all of your problems.

    If the pin is NOT in there -- you may have to make one. I've heard of people making a pin out of clothes hangar metal. The exact length of the pin is 1.450" as per the following thread:
    http://www.explorerforum.com/forums/index.php?threads/a4ld-vacuum-modulator-pin-length.443343/

    Also the below thread has pics of the modulator and part of the pin sticking out of it. That pin DOES fall out and is a separate piece:
    http://www.explorerforum.com/forums...-through-the-access-panel-center-hump.263904/
     
  11. paulha

    paulha Member

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    Rhett, thanks for the comeback and all the great info and links. Latest update is I have gotten the modulator out and the pin was in there! Wahoo! I am now trying to install a new one, my question is should there be any tension against the new one, or should it just push in? Is it possible to put the pin in and have it not be in the hole in the plunger in the tranny? Seems like there is some tension against the modulator as I try to push it in?
     
  12. transman304

    transman304 Elite Explorer

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    There will be tension as you install the modulator.
     
  13. paulha

    paulha Member

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    Finally got that durn thing in there and I am mobile again. That was a real nightmare! So now it runs some better, still shifts hard sometimes and has to get the rpms up there to shift. Right now it shifts from 1st to 2nd at 35Mph/3300 rpms and doesn't go into 3 or OD until
    55-60mph and 4000-4500 rpms. Sure not as smooth and quick to shift as before. What can I do to smooth this out and get the shift rpms down? Also what are the normal shift points? You guys have been a tremendous help and led me step by step and I really appreciate it more than I can say.
     
  14. Rhett

    Rhett Let Them Eat Cake Elite Explorer

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    Did you install an adjustable modulator?
     
  15. paulha

    paulha Member

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    Yes sir I did
     
  16. Rhett

    Rhett Let Them Eat Cake Elite Explorer

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    Oh, well then use the adjustment! On mine, there is a little wheel you turn to adjust it, located on the modulator body.

    Also make sure the modulator is getting good vacuum from the manifold. If it is not -- it can't do its job.
     
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  17. paulha

    paulha Member

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    Mine doesn't have a wheel but does have an allen screw. just how exactly do you know which way and how much? Or is it just a little this way then a little that way? Is there any way to tell what you are doing or do you just drive it to find out?
     
  18. Rhett

    Rhett Let Them Eat Cake Elite Explorer

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    I can't speak for your adjustable, but as I recall on mine counterclockwise = lower 1-2 shift rpm. Turn it one way (pick a way -- counterclockwise or clockwise...), then drive. I would hold the modulator with one hand, while you turn the allen, so that you do not work the modulator loose adjusting it.

    If you turn it, say, counterclockwise, and your 1-2 shift is lower, then you'll know you're doing it right. I don't know of any easier way to do it.
     
  19. paulha

    paulha Member

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    Sorry for the delay in finishing this saga, but here is the final solution. I had bought both the original and the replacement Vacuum Modulator at O'Rielly's. Finally in total frustration took her to AAMCO and had it checked out. Turns out that the two modulators from O'Riellys were pulling too much vacuum so wouldn't shift. They put in a replacement of their own (costs about twice of O'Rielly's) and vwalla!! It shifts so smooth you can't even feel it. Thank everyone for their help and advice and I hope this can help someone else. This group is really awesome.
     
  20. CDW6212R

    CDW6212R Hauls the mail. Elite Explorer

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    Interesting. I didn't know of an adjustable modulator when I did mine in 1998. I changed it in my 91 as preventative maintenance, plus a VB kit, which all helped. I was recommended to install a longer pin too, which I did. That adjustable unit probably does the same thing. I went to a friend trans shop, and he gave me one from some old Dodge application. The trick was that it's 1/8" longer than the original. We used the old one to identify a longer version. I did the same thing with my old 93 next in about 2000. It all helped to firm up the shifts, and the A4LD needs all the help it can get.
     
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  21. Rhett

    Rhett Let Them Eat Cake Elite Explorer

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    Auto store parts these days. I bought some bleeder valves the other day, and they were those "speed bleeder" type. They were terrible. Once open, neither one would close up. I had to go get the traditional type of bleeder valve. And clean my garage floor.

    Anyway, I'm glad you figured out the modulator issue. You know all about it now, and can help someone else!
     






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